Exhaust valve, exhaust valve assembly and exhaust valve system for two-stroke internal combustion engines, two-stroke internal combustion engine having same and method for cleaning an exhaust valve

ABSTRACT

An exhaust valve system for a two-stroke internal combustion engine having: at least one exhaust valve movable between open and closed positions; an actuator for moving the at least one exhaust valve; a valve position sensor; a controller communicating with the actuator and the valve position sensor. The controller being programmed for: controlling the actuator to attempt to move the at least one exhaust valve to a desired one of the open and closed positions; determining if the at least one exhaust valve has failed to reach the desired position based on the position of the at least one exhaust valve sensed by the valve position sensor; and controlling the actuator to move the at least one exhaust valve to an intermediate position when the at least one exhaust valve has failed to reach the desired position.

CROSS-REFERENCE

The present application is a divisional of U.S. patent application Ser.No. 16/915,876, filed Jun. 29, 2020, which claims priority to U.S.Provisional Patent Application No. 62/868,764, filed Jun. 28, 2019; U.S.Provisional Patent Application No. 62/868,768, filed Jun. 28, 2019; U.S.Provisional Patent Application No. 62/868,770, filed Jun. 28, 2019; U.S.Provisional Patent and Application No. 62/894,731, filed Aug. 31, 2019,the entirety of each of which is incorporated herein by reference.

FIELD OF TECHNOLOGY

The present technology relates to exhaust valves, exhaust valveassemblies and exhaust valve systems for two-stroke internal combustionengines, to two-stroke internal combustion engines having same and tomethods for cleaning an exhaust valve of an exhaust valve system for atwo-stroke internal combustion engine.

BACKGROUND

In two-stroke internal combustion engines, exhaust valves are used toalter the exhaust timing in order to tune the power provided by theengine over a wide range of engine speeds. Different types of exhaustvalves exist. One such type of exhaust valve is the reciprocatingexhaust valve.

A reciprocating exhaust valve is provided at least in part in an exhaustvalve passage that communicates with the exhaust passage of a cylinderof the engine. The exhaust valve has a shaft connected to an actuatorand a blade connected to the shaft. The actuator slides the exhaustvalve in the exhaust valve passage between various positions. In one ormore such positions, the blade is received at least in part in theexhaust passage to block a portion of the exhaust passage, therebychanging the exhaust timing.

The exhaust gases contain various components, such as loose oily exhaustsoot, that can deposit on the blade of the exhaust valve and the wallsof the exhaust valve passage. The exhaust gas components may carbonize,or coke, on the blade of the exhaust valve and the walls of the exhaustvalve passage when a sufficiently high temperature is reached. Thesecarbonized, or coked, deposits can impede movement of the exhaust valve.

In order to prevent the above from happening, the exhaust valves andexhaust valve passages typically need to be cleaned periodically. Thistypically requires disassembly of the exhaust valves and its associatedcomponents from the engine. This is inconvenient, time consuming andtypically too complex for a user of the engine to do himself/herself. Assuch, this cleaning is typically done by a qualified mechanic.

One solution used by engineers designing engines with reciprocatingexhaust valves has been to make the clearance between the blade of theexhaust valve and the walls of the exhaust valve passage as small aspossible. This limits the exposure of the blade to the exhaustcomponents that could carbonize, or coke.

Another solution consists in making the exhaust valve from a materialhaving a relatively high thermal conductivity, such as aluminum. As aresult, heat is quickly conducted away from the blade to the shaft ofthe exhaust valve and other surrounding components, in an attempt tokeep the temperature of the blade below the carbonization, or coking,temperature of the exhaust components that deposit on the blade, therebypreventing carbonization, or coking, from occurring.

Although such solutions are adequate for applications where the engineis often used at relatively high engine speeds, such as in snowmobilesand motocross, they can prove to be insufficient for applications wherethe engine is often used at relatively low speeds, such as in marineoutboard engines that are often used at trolling speeds.

There is therefore a desire for a reciprocating exhaust valve for atwo-stroke engine that addresses the problem of exhaust componentdeposits described above.

There is therefore also a desire for a two-stroke engine having areciprocating exhaust valve that addresses the problem of exhaustcomponent deposits described above.

There is therefore also a desire for an exhaust valve for a two-strokeinternal combustion engine and a method for cleaning an exhaust valve ofsuch a system that address the problem of cleaning exhaust componentdeposits from the exhaust valve described above.

In some engines, the exhaust valves are actuated by pressure inside thecrankcase of the engine. In other engines, a governor connected to acrankshaft of the engine operates a clutch that in turn actuates theexhaust valves as the engine speed goes above or below a thresholdengine speed. Although adequate, these actuators limit the degree ofcontrol of the exhaust valves.

In other engines, an electric motor drives a hydraulic pump and theexhaust valves are hydraulically actuated. Although this permits morecontrol of the exhaust valves, the hydraulic pump and all of theassociated hydraulic components required make this a complex and bulkysystem.

In yet other engines, an electric motor is connected via a push-pullcable to the exhaust valves. The push-pull cable is provided in order topermit mounting of the electric motor remotely from the engine in orderto isolate it from engine heat and vibrations. Although this permitsmore control of the exhaust valves, in some applications, such as inmarine outboard engine, it is not possible to mount the electric motorremotely from the engine and/or it is not easily feasible to properlyroute the push-pull cable.

There is therefore also a desire for an exhaust valve assembly for atwo-stroke engine that addresses the problems described above.

SUMMARY

It is an object of the present technology to ameliorate at least some ofthe inconveniences present in the prior art.

Contrary to the above-described prior art solutions which attempt tolimit the exposure of the exhaust valve to the exhaust gas and to limitthe temperature of the blade of the exhaust valve, the presenttechnology takes a diametrically opposite approach. The presenttechnology increases the exposure of the blade of the exhaust gases andbuild up heat in the blade in an attempt to have the temperature of theportions of the blade where carbon can build up reach the carbonburn-off temperature under at least some operating conditions of theengine. The carbon burn-off temperature is higher than thecarbonization, or coking, temperature of the exhaust gas components.When the carbon burn-off temperature is reached, the carbonizedcomponents burn-off the blade or crack, crumble and fall away from theblade, thereby cleaning the blade of the exhaust valve.

In one aspect of the present technology, this is achieved by providingan exhaust valve having a blade defining a channel that together with awall of an exhaust valve passage inside which the exhaust valve isdisposed define a valve passage. Due to the relatively large size of thevalve passage, a substantial flow of exhaust gases along the face of theblade defining the channel is permitted which permits the exhaust gases,under certain operating conditions of the engine, to heat the bladeabove the carbon burn-off temperature of exhaust components that mayhave accumulated on the blade. Also, the size of the valve passage doesnot promote the compaction of the exhaust gas components between theblade and the wall of the exhaust valve passage and permits thesecomponents to fall into the exhaust passage of the cylinder block as theexhaust valve reciprocates.

In another aspect of the present technology, this is achieved byproviding a blade having thinner portions where heat can build up. Insome embodiments, the blade is made of a material having a relativelylow thermal conductivity, such as stainless steel for example.

According to one aspect of the present technology, there is provided atwo-stroke internal combustion engine having an engine block having acylinder block and a cylinder head. The cylinder block defines: acylinder defining a cylinder axis; an exhaust passage communicating withthe cylinder; and an exhaust valve passage communicating with theexhaust passage, the exhaust valve passage having a first wall and asecond wall. The cylinder head is connected to the cylinder block. Thefirst wall of the exhaust valve passage is closer to the cylinder headthan the second wall of the exhaust valve passage in a direction definedby the cylinder axis. The engine also has a piston disposed in thecylinder; an exhaust valve actuator operatively connected to at leastone of the cylinder block and the cylinder head; and a reciprocatingexhaust valve disposed at least in part in the exhaust valve passage.The reciprocating exhaust valve has a shaft operatively connected to avalve actuator, the shaft defining a reciprocation axis of the valve,the reciprocation axis defining a longitudinal direction of the valve;and a blade. The blade has a first end having an arcuate edge; a secondend opposite the first end, the shaft being connected to the second end;a first face facing the first wall of the exhaust valve passage; and asecond face opposite the first face, the second face facing the secondwall of the exhaust valve passage. Each of the first and second facesextends between the first and second ends. A channel is defined alongthe second face. The channel extends in the longitudinal direction. Thechannel and the second wall of the exhaust valve passage together defineat least in part a valve passage. The valve passage permits flow ofexhaust gas from the first end of the blade to the second end of theblade. A width of the valve passage is at least a third of a width ofthe blade. The width of the valve passage and the width of the blade aremeasured in a lateral direction. The lateral direction is perpendicularto the longitudinal direction.

In some embodiments of the present technology, the width of the valvepassage is at least half of the width of the blade.

In some embodiments of the present technology, the channel is a firstchannel. A second channel is defined along the second face. The secondchannel extends in the longitudinal direction. The first and secondchannels are disposed on opposite sides of the reciprocation axis. Thevalve passage is defined at least in part by the first channel, thesecond channel and the second wall of the exhaust valve passage.

In some embodiments of the present technology, a majority of the firstface is flat.

In some embodiments of the present technology, the blade has a first endportion adjacent the first end; a second end portion adjacent the secondend; and a mid-portion disposed longitudinally between the first andsecond end portions. A thickness of a part of the second end portiondefining the channel is less than a thickness of a part of themid-portion defining the channel. The thickness of the part of thesecond end portion and of the part of the mid-portion is measured in adirection perpendicular to the longitudinal and lateral directions.

In some embodiments of the present technology, the shaft defines astopper.

In some embodiments of the present technology, the stopper is in slidingfit with the exhaust valve passage.

In some embodiments of the present technology, a clearance between thestopper and a portion of the cylinder block defining the exhaust valvepassage is less than a minimum clearance between the blade and theportion of the cylinder block defining the exhaust valve passage.

In some embodiments of the present technology, a maximum thickness ofthe passage is at least one third of a diameter of the stopper. Thethickness of the passage is measured in a direction perpendicular to thelongitudinal and lateral directions.

In some embodiments of the present technology, the cylinder is aplurality of cylinder; the exhaust passage is a plurality of exhaustpassages, each exhaust passage of the plurality of exhaust passagescommunicating with a corresponding cylinder of the plurality ofcylinder; the exhaust valve passage is a plurality of exhaust passages,each exhaust valve passage of the plurality of exhaust valve passagescommunicating with a corresponding exhaust passage of the plurality ofexhaust passages; the piston is a plurality of pistons, each piston ofthe plurality of pistons is disposed in a corresponding cylinder of theplurality of cylinders; and the reciprocating exhaust valve is aplurality of reciprocating exhaust valves, each reciprocating exhaustvalve of the plurality of reciprocating exhaust valves being disposed atleast in part in a corresponding exhaust valve passage of the pluralityof exhaust valve passages.

In some embodiments of the present technology, each reciprocatingexhaust valve of the plurality of reciprocating exhaust valves isoperatively connected to the exhaust valve actuator.

According to another aspect of the present technology, there is provideda reciprocating exhaust valve for a two-stroke internal combustionengine having a shaft for connection to a valve actuator, the shaftdefining a reciprocation axis of the valve, the reciprocation axisdefining a longitudinal direction of the valve; and a blade having afirst end and a second end opposite the first end. The shaft isconnected to the second end of the blade. The first end has an arcuateedge. The blade has two side portions and a central portion. The centralportion is disposed between the two side portions in a lateral directionof the valve. The lateral direction is perpendicular to the longitudinaldirection. The blade has a first end portion adjacent the first end. Thefirst end portion includes a part of the central portion and a part ofeach of the two side portions. A width of the central portion is greaterthan a width of each of the side portions. The width of the centralportion and the width of each of the side portions is measured in thelateral direction. A thickness of the part of each of the two sideportions in the first end portion is greater than a thickness of thepart of the central portion in the first end portion. The thickness ofeach of the side portions and the thickness of the central portion ismeasured in a direction perpendicular to the longitudinal and lateraldirections.

In some embodiments of the present technology, the width of the centralportion is greater than a sum of the widths of the two side portions.

In some embodiments of the present technology, the width of the centralportion is greater than half of a width of the blade, the width of theblade being measured in the lateral direction.

In some embodiments of the present technology, the blade has a firstface and a second face opposite the first face. Each of the first andsecond faces extends between the first and second ends. A majority ofthe first face is flat. The blade has a reinforcing structure providedon the second face.

In some embodiments of the present technology, the reinforcing structureis a plurality of ribs.

In some embodiments of the present technology, a cross-section of eachof the two side portions is generally semi-circular, the cross-sectionbeing taken through a plane extending in the lateral direction and beingnormal to the reciprocation axis.

In some embodiments of the present technology, the blade has a firstface and a second face opposite the first face. Each of the first andsecond faces extends between the first and second ends. A majority ofthe first face is flat. The two side portions are a first side portionand a second side portion. A first channel is defined along the secondface adjacent to the first side portion. The first side portion and thecentral portion define at least in part the first channel. The firstchannel is disposed completely on a same side of the reciprocation axisas the first side portion. A second channel is defined along the secondface adjacent to the second side portion. The second side portion andthe central portion define at least in part the second channel. Thesecond channel is disposed completely on a same side of thereciprocation axis as the second side portion. The first and secondchannels extend in the longitudinal direction.

In some embodiments of the present technology, the blade has amid-portion adjacent the first end portion and disposed longitudinallybetween the first end portion and the second end of the blade. Themid-portion includes another part of the central portion and anotherpart of each of the two side portions. A thickness of the other part ofthe central portion in the mid-portion is greater than the thickness ofthe part of the central portion in the first end portion.

In some embodiments of the present technology, the shaft defines astopper.

In some embodiments of the present technology, the shaft includes: afirst shaft portion for connection to the valve actuator; and a secondshaft portion connected to the second end of the blade. The first shaftportion has a first diameter. At least part of the second shaft portionhas a second diameter defining the stopper. The second diameter isgreater than the first diameter.

In some embodiments of the present technology, the blade is astainless-steel blade.

In some embodiments of the present technology, the blade and the shaftare integral.

According to another aspect of the present technology, there is provideda two-stroke internal combustion engine having an engine block defining:a cylinder; an exhaust passage communicating with the cylinder; and anexhaust valve passage communicating with the exhaust passage. The enginealso has a piston disposed in the cylinder, the reciprocating exhaustvalve of any one of the above aspect and embodiments disposed at leastin part in the exhaust valve passage, and an exhaust valve actuatoroperatively connected to the exhaust valve for moving the blade of theexhaust valve in the exhaust passage.

According to another aspect of the present technology, the is provided areciprocating exhaust valve for a two-stroke internal combustion enginehaving a shaft for connection to a valve actuator, the shaft defining areciprocation axis of the valve, the reciprocation axis defining alongitudinal direction of the valve; and a blade having a first end anda second end opposite the first end. The first end has an arcuate edge.The blade has two side portions and a central portion. The centralportion is disposed between the two side portions in a lateral directionof the valve. The lateral direction is perpendicular to the longitudinaldirection. The central portion has two central sub-portions adjacent thesecond end. The shaft is connected to the second end laterally betweenthe two central sub-portions. The central portion has a centralmid-portion adjacent the two central sub-portion and disposedlongitudinally between the two central sub-portions and the first end ofthe blade. A thickness of each of the two central sub-portions is lessthan a thickness of the central mid-portion. The thickness of each ofthe two central sub-portions and the thickness of the centralmid-portion are measured in a direction perpendicular to thelongitudinal and lateral directions.

In some embodiments of the present technology, the second end has twoarcuate edges. The shaft is connected to the second end laterallybetween the two arcuate edges.

In some embodiments of the present technology, the blade also has afirst flange connected to and extending perpendicularly to one of thetwo central sub-portions; and a second flange connected to and extendingperpendicularly to another one of the two central sub-portions. Thefirst and second flanges are adjacent to the second end.

In some embodiments of the present technology, the blade has a firstface and a second face opposite the first face. Each of the first andsecond faces extends between the first and second ends. A majority ofthe first face is flat. The blade has a reinforcing structure providedon the second face.

In some embodiments of the present technology, the reinforcing structureis a plurality of ribs.

In some embodiments of the present technology, the blade has a firstface and a second face opposite the first face. Each of the first andsecond faces extends between the first and second ends. A majority ofthe first face is flat. The two side portions are a first side portionand a second side portion. A first channel is defined along the secondface adjacent to the first side portion. The first side portion and thecentral portion define at least in part the first channel. The firstchannel is disposed completely on a same side of the reciprocation axisas the first side portion. A second channel is defined along the secondface adjacent to the second side portion. The second side portion andthe central portion define at least in part the second channel. Thesecond channel is disposed completely on a same side of thereciprocation axis as the second side portion. The first and secondchannels extend in the longitudinal direction.

In some embodiments of the present technology, a thickness of a part ofthe central portion disposed laterally between the two centralsub-portions is greater than the thickness of each of the two centralsub-portions. The thickness of the part of the central portion ismeasured in the direction perpendicular to the longitudinal and lateraldirections.

In some embodiments of the present technology, the shaft defines astopper.

In some embodiments of the present technology, the shaft includes afirst shaft portion for connection to the valve actuator; and a secondshaft portion connected to the second end of the blade. The first shaftportion has a first diameter. At least part of the second shaft portionhas a second diameter defining the stopper. The second diameter isgreater than the first diameter.

In some embodiments of the present technology, the blade is astainless-steel blade.

In some embodiments of the present technology, the blade and the shaftare integral.

According to another aspect of the present technology, there is provideda two-stroke internal combustion engine having an engine block defining:a cylinder; an exhaust passage communicating with the cylinder; and anexhaust valve passage communicating with the exhaust passage. The enginealso has a piston disposed in the cylinder; the reciprocating exhaustvalve of any one of the above aspect and embodiments disposed at leastin part in the exhaust valve passage; and an exhaust valve actuatoroperatively connected to the exhaust valve for moving the blade of theexhaust valve in the exhaust passage.

In another aspect, the present technology determines that exhaustcomponents have likely deposited on the exhaust valve when the exhaustvalve fails to reach its desired position (open or closed). When thishappens, the exhaust valve is moved to an intermediate position wherethe exhaust valve is exposed to the exhaust gases. As a result, heatbuilds up in the exhaust valve in an attempt to have the temperature ofthe portions of the exhaust valve where carbon can build up reach thecarbon burn-off temperature under at least some operating conditions ofthe engine. The carbon burn-off temperature is higher than thecarbonization, or coking, temperature of the exhaust gas components.When the carbon burn-off temperature is reached, the carbonizedcomponents burn-off the exhaust valve or crack, crumble and fall awayfrom the exhaust valve, thereby cleaning the exhaust valve.

According to another aspect of the present technology, there is providedan exhaust valve system for a two-stroke internal combustion enginehaving: at least one exhaust valve movable between an open position anda closed position; an actuator operatively connected to the at least oneexhaust valve for moving the at least one exhaust valve between the openposition and the closed position; a valve position sensor fordetermining a position of the at least one exhaust valve; and acontroller communicating with the actuator for controlling the actuator,the controller communicating with the valve position sensor forreceiving a signal indicative of the position of the at least oneexhaust valve. The controller is programmed for: a) controlling theactuator to attempt to move the at least one exhaust valve to a desiredone of the open position and the closed position; b) determining if theat least one exhaust valve has failed to reach the desired one of theopen position and the closed position based on the position of the atleast one exhaust valve sensed by the valve position sensor; and c)controlling the actuator to move the at least one exhaust valve to anintermediate position when the at least one exhaust valve has failed toreach the desired one of the open position and the closed position, theintermediate position of the at least one exhaust valve being betweenthe open position and the closed position.

According to some embodiments of the present technology, determining ifthe at least one exhaust valve has failed to reach the desired one ofthe open position and the closed position comprises comparing theposition of the at least one exhaust valve sensed by the valve positionsensor to the desired one of the open position and the closed position.

According to some embodiments of the present technology, controlling theactuator to move the at least one exhaust valve to the intermediateposition comprises controlling the actuator to move the at least oneexhaust valve to the intermediate position for a predetermined amount oftime. Once the at least one exhaust valve has been in the intermediateposition for the predetermined amount of time, the controller is furtherprogrammed for: d) controlling the actuator to reattempt to move the atleast one exhaust valve to the desired one of the open position and theclosed position; and e) comparing the position of the at least oneexhaust valve sensed by the valve position sensor to the desired one ofthe open position and the closed position to determine if the at leastone exhaust valve has failed again to reach the desired one of the openposition and the closed position.

According to some embodiments of the present technology, controlling theactuator to move the at least one exhaust valve to the intermediateposition comprises controlling the actuator to move the at least oneexhaust valve to the intermediate position for a predetermined amount oftime. Once the at least one exhaust valve has been in the intermediateposition for the predetermined amount of time, the controller is furtherprogrammed for: d) controlling the actuator to reattempt to move the atleast one exhaust valve to the desired one of the open position and theclosed position.

According to some embodiments of the present technology, subsequent tostep d), the controller is further programmed for: e) determining if theat least one exhaust valve has failed to reach the desired one of theopen position and the closed position based on the position of the atleast one exhaust valve sensed by the valve position sensor.

According to some embodiments of the present technology, if at step e)the controller determines that the at least one exhaust valve has failedagain to reach the desired one of the open position and the closedposition, the controller is further programmed for: f) controlling theactuator to move the at least one exhaust valve to the intermediateposition for the predetermined amount of time; and then g) repeatingsteps d) and e), and, if the at least one exhaust valve has failed againto reach the desired one of the open position and the closed position,step f), until: the controller determines at a subsequent instance ofstep e) that the at least one exhaust valve has not failed to reach thedesired one of the open position and the closed position; or steps d)and e) have been repeated a predetermined number of times with the atleast one exhaust valve having failed each time to reach the desired oneof the open position and the closed position.

According to some embodiments of the present technology, thepredetermined amount of time is a first predetermined amount of time. Ifsteps d) and e) have been repeated the first predetermined number oftimes with the at least one exhaust valve having failed each time toreach the desired one of the open position and the closed position, thecontroller is further programmed for: h) maintaining the at least oneexhaust valve in a current position for a second predetermined amount oftime, then controlling the actuator to move the at least one exhaustvalve to the intermediate position for a third predetermined amount oftime, the second predetermined amount of time being greater than thefirst predetermined amount of time, the third predetermined amount oftime being less than the first predetermined amount of time; i)controlling the actuator to reattempt to move the at least one exhaustvalve to the desired one of the open position and the closed position;j) determining if the at least one exhaust valve has failed again toreach the desired one of the open position and the closed position basedon the position of the at least one exhaust valve sensed by the valveposition sensor; and k) repeating steps i) and j), and, if the at leastone exhaust valve has failed again to reach the desired one of the openposition and the closed position, step h), until the controllerdetermines at step j) that the at least one exhaust valve has not failedto reach the desired one of the open position and the closed position.

According to some embodiments of the present technology, the controlleris further programmed for: l) performing step c) and any subsequentsteps only if at step b): the controller determines that the at leastone exhaust valve has failed to reach the desired one of the openposition and the closed position; and the position of the at least oneexhaust valve is at less than a predetermined distance from the desiredone of the open position and the closed position. If at step b): thecontroller determines that the at least one exhaust valve has failed toreach the desired one of the open position and the closed position; andthe position of the at least one exhaust valve is at more than thepredetermined distance from the desired one of the open position and theclosed position, then the controller is programmed for: m) controllingthe actuator to move the at least one exhaust valve to one of the openposition and the closed position other than the desired one of the openposition and the closed position; and n) returning to step a).

According to some embodiments of the present technology, step m)comprises maintaining the at least one exhaust valve in the one of theopen position and the closed position other than the desired one of theopen position and the closed position for a predetermined amount of timebefore performing step n).

According to some embodiments of the present technology, at step m) thepredetermined amount of time before performing step n) is an amount oftime for which the internal combustion engine has been operating above apredetermined engine speed.

According to some embodiments of the present technology, the controlleris further programmed for maintaining the at least one exhaust valve inthe one of the open and the closed position other than the desired oneof the open position and the closed position until the internalcombustion engine is turned off if step m) has been performed apredetermined number of time.

According to some embodiments of the present technology, the desired oneof the open position and the closed position is the open position.

According to some embodiments of the present technology, thepredetermined amount of time is greater when the desired one of the openposition and the closed position is the open position than when thedesired one of the open position and the closed position is the closedposition.

According to some embodiments of the present technology, theintermediate position is or is approximately halfway between the openposition and the closed position.

According to some embodiments of the present technology, in theintermediate position the at least one exhaust valve does not affectport timing of the internal combustion engine and is exposed to exhaustgas flow.

According to some embodiments of the present technology, each of the atleast one exhaust valve comprises a blade.

According to some embodiments of the present technology, the at leastone exhaust valve is at least one reciprocating exhaust valve.

According to some embodiments of the present technology, the actuator isa linear actuator.

According to some embodiments of the present technology, the actuator isan electrical actuator.

According to some embodiments of the present technology, the valveposition sensor senses a position of the actuator for determining theposition of the at least one exhaust valve.

According to some embodiments of the present technology, the at leastone exhaust valve is a plurality of exhaust valves.

According to some embodiments of the present technology, the controllerdetermines that the at least one exhaust valve has failed to reach thedesired one of the open position and the closed position if the positionof the at least one exhaust valve is at more than a predetermineddistance from the desired one of the open position and the closedposition.

According to some embodiments of the present technology, thepredetermined distance is greater when the desired one of the openposition and the closed position is the open position than when thedesired one of the open position and the closed position is the closedposition.

According to some embodiments of the present technology, thepredetermined distance is at least 5 percent of a total distance betweenthe open position and the closed position.

According to some embodiments of the present technology, the controlleris further programmed for: entering a fault operation mode if, inresponse to the actuator attempting to move the at least one exhaustvalve to the desired one of the open position and the closed position,the at least one exhaust valve has moved by less than a predeterminedamount.

According to some embodiments of the present technology, thepredetermined amount corresponds to 5 percent of a total distancebetween the open position and the closed position.

According to some embodiments of the present technology, in the faultoperation mode, the controller limits performance of the engine providedwith the exhaust valve system.

In another aspect of the present technology, there is provided a methodfor cleaning at least one exhaust valve of an exhaust valve system for atwo-stroke internal combustion system. The method comprises: a)controlling an actuator operatively connected to the at least oneexhaust valve to attempt to move the at least one exhaust valve to adesired one of an open position and a closed position; b) determining ifthe at least one exhaust valve has failed to reach the desired one ofthe open position and the closed position based on a position of the atleast one exhaust valve sensed by a valve position sensor; and c)controlling the actuator to move the at least one exhaust valve to anintermediate position when the at least one exhaust valve has failed toreach the desired one of the open position and the closed position, theintermediate position of the at least one exhaust valve being betweenthe open position and the closed position.

According to some embodiments of the present technology, determining ifthe at least one exhaust valve has failed to reach the desired one ofthe open position and the closed position comprises comparing theposition of the at least one exhaust valve sensed by the valve positionsensor to the desired one of the open position and the closed position.

According to some embodiments of the present technology, controlling theactuator to move the at least one exhaust valve to the intermediateposition comprises controlling the actuator to move the at least oneexhaust valve to the intermediate position for a predetermined amount oftime. Once the at least one exhaust valve has been in the intermediateposition for the predetermined amount of time: d) controlling theactuator to reattempt to move the at least one exhaust valve to thedesired one of the open position and the closed position; and e)comparing the position of the at least one exhaust valve sensed by thevalve position sensor to the desired one of the open position and theclosed position to determine if the at least one exhaust valve hasfailed again to reach the desired one of the open position and theclosed position.

According to some embodiments of the present technology, controlling theactuator to move the at least one exhaust valve to the intermediateposition comprises controlling the actuator to move the at least oneexhaust valve to the intermediate position for a predetermined amount oftime. Once the at least one exhaust valve has been in the intermediateposition for the predetermined amount of time: d) controlling theactuator to reattempt to move the at least one exhaust valve to thedesired one of the open position and the closed position.

According to some embodiments of the present technology, subsequent tostep d): e) determining if the at least one exhaust valve has failed toreach the desired one of the open position and the closed position basedon the position of the at least one exhaust valve sensed by the valveposition sensor.

According to some embodiments of the present technology, if at step e)the controller determines that the at least one exhaust valve has failedagain to reach the desired one of the open position and the closedposition: f) controlling the actuator to move the at least one exhaustvalve to the intermediate position for the predetermined amount of time;and then g) repeating steps d) and e), and, if the at least one exhaustvalve has failed again to reach the desired one of the open position andthe closed position, step f), until: the controller determines at asubsequent instance of step e) that the at least one exhaust valve hasnot failed to reach the desired one of the open position and the closedposition; or steps d) and e) have been repeated a predetermined numberof times with the at least one exhaust valve having failed each time toreach the desired one of the open position and the closed position.

According to some embodiments of the present technology, thepredetermined amount of time is a first predetermined amount of time. Ifsteps d) and e) have been repeated the first predetermined number oftimes with the at least one exhaust valve having failed each time toreach the desired one of the open position and the closed position: h)maintaining the at least one exhaust valve in a current position for asecond predetermined amount of time, then controlling the actuator tomove the at least one exhaust valve to the intermediate position for athird predetermined amount of time, the second predetermined amount oftime being greater than the first predetermined amount of time, thethird predetermined amount of time being less than the firstpredetermined amount of time; i) controlling the actuator to reattemptto move the at least one exhaust valve to the desired one of the openposition and the closed position; j) determining if the at least oneexhaust valve has failed again to reach the desired one of the openposition and the closed position based on the position of the at leastone exhaust valve sensed by the valve position sensor; and k) repeatingsteps i) and j), and, if the at least one exhaust valve has failed againto reach the desired one of the open position and the closed position,step h), until the controller determines at step j) that the at leastone exhaust valve has not failed to reach the desired one of the openposition and the closed position.

According to some embodiments of the present technology, the methodfurther comprises l) performing step c) and any subsequent steps only ifat step b): the controller determines that the at least one exhaustvalve has failed to reach the desired one of the open position and theclosed position; and the position of the at least one exhaust valve isat less than a predetermined distance from the desired one of the openposition and the closed position. If at step b): the controllerdetermines that the at least one exhaust valve has failed to reach thedesired one of the open position and the closed position; and theposition of the at least one exhaust valve is at more than thepredetermined distance from the desired one of the open position and theclosed position, then m) controlling the actuator to move the at leastone exhaust valve to one of the open position and the closed positionother than the desired one of the open position and the closed position;and n) returning to step a).

According to some embodiments of the present technology, step m)comprises maintaining the at least one exhaust valve in the one of theopen position and the closed position other than the desired one of theopen position and the closed position for a predetermined amount of timebefore performing step n).

According to some embodiments of the present technology, at step m) thepredetermined amount of time before performing step n) is an amount oftime for which the internal combustion engine has been operating above apredetermined engine speed.

According to some embodiments of the present technology, the methodfurther comprises maintaining the at least one exhaust valve in the oneof the open and the closed position other than the desired one of theopen position and the closed position until the internal combustionengine is turned off if step m) has been performed a predeterminednumber of time.

According to some embodiments of the present technology, the desired oneof the open position and the closed position is the open position.

According to some embodiments of the present technology, thepredetermined amount of time is greater when the desired one of the openposition and the closed position is the open position than when thedesired one of the open position and the closed position is the closedposition.

According to some embodiments of the present technology, theintermediate position is or is approximately halfway between the openposition and the closed position.

According to some embodiments of the present technology, in theintermediate position the at least one exhaust valve does not affectport timing of the internal combustion engine and is exposed to exhaustgas flow.

According to some embodiments of the present technology, the at leastone exhaust valve is determined to have failed to reach the desired oneof the open position and the closed position if the position of the atleast one exhaust valve is at more than a predetermined distance fromthe desired one of the open position and the closed position.

According to some embodiments of the present technology, thepredetermined distance is greater when the desired one of the openposition and the closed position is the open position than when thedesired one of the open position and the closed position is the closedposition.

According to some embodiments of the present technology, thepredetermined distance is at least 5 percent of a total distance betweenthe open position and the closed position.

According to some embodiments of the present technology, the methodfurther comprises: entering a fault operation mode if, in response tothe actuator attempting to move the at least one exhaust valve to thedesired one of the open position and the closed position, the at leastone exhaust valve has moved by less than a predetermined amount.

According to some embodiments of the present technology, thepredetermined amount corresponds to 5 percent of a total distancebetween the open position and the closed position.

According to some embodiments of the present technology, the methodfurther comprises limiting performance of the engine provided with theexhaust valve system when in the fault operation mode.

In another aspect, the present technology provides an exhaust valveassembly for a two-stroke internal combustion engine having a housingthat is to be mounted to the engine block of the engine, an electricactuator is disposed in the housing and is connected to at least onereciprocating exhaust valve that extends in part into the housing. Theelectric motor provides for versatile control of the exhaust valves. Bylocating the electric motor inside the housing, the electric motor ispartly isolated from engine heat and vibration. In some embodiments, theelectric motor is mounted to the housing via a vibration absorbing mountfurther isolating the electric actuator from vibrations. In someembodiments, the at least one exhaust valve is connected to the electricactuator via a vibration absorbing mount further isolating the electricactuator from vibrations.

According to one aspect of the present technology, there is provided anexhaust valve assembly for a two-stroke internal combustion engine. Theexhaust valve assembly has: a housing adapted for connection to anengine block of the two-stroke internal combustion engine; an electricactuator comprising an electric motor, the electric motor being disposedin the housing; and at least one reciprocating exhaust valve operativelyconnected to the electric actuator, the at least one exhaust valve beinglinearly movable by the electric motor, and a portion of the at leastone exhaust valve being disposed in the housing.

In some embodiments of the present technology, each exhaust valve of theat least one exhaust valve has a blade and a shaft connected to theblade. The portion of the at least one exhaust valve being disposed inthe housing is a portion of the shaft.

In some embodiments of the present technology, the housing includes: ahousing body; and a base plate connected to the housing body. Theelectric motor is disposed in a volume defined between the housing bodyand the base plate. The base plate is disposed between the housing bodyand the blade of each of the at least one exhaust valve.

In some embodiments of the present technology, the shaft of each of theat least one exhaust valve extends through the base plate.

In some embodiments of the present technology, at least one pair ofexhaust valve passage fillers connected to the base plate for filling aportion of at least one exhaust valve passage defined by the engineblock for receiving the at least one exhaust valve. The least one pairof exhaust valve passage fillers is disposed between the base plate andthe blade of the at least one exhaust valve. The shaft of the at leastone exhaust valve extends between the exhaust valve passage fillers ofthe at least one pair of exhaust valve passage fillers.

In some embodiments of the present technology, the at least one pair ofexhaust valve passage fillers are integral with the base plate.

In some embodiments of the present technology, for each exhaust valve ofthe at least one exhaust valve, the housing includes a seal disposedbetween the base plate and the shaft of the at least one exhaust valve.

In some embodiments of the present technology, a vibration absorbingmount connects the electric actuator to the housing.

In some embodiments of the present technology, the housing includes: ahousing body; and a cover connected to the housing body. The housingbody is disposed at least in part between the blade of the at least onevalve and the cover. The vibration absorbing mount connects the electricactuator to the cover.

In some embodiments of the present technology, the electric actuatoralso has a lead screw operatively connecting the at least one exhaustvalve to an output shaft of the electric motor for converting rotationof the output shaft to linear motion.

In some embodiments of the present technology, the lead screw and theoutput shaft are parallel to each other.

In some embodiments of the present technology, a vibration absorbingmount connects the at least one exhaust valve to the electric actuator.

In some embodiments of the present technology, a tie bar is connected tothe electric actuator. The at least one exhaust valve is a plurality ofexhaust valves. Each exhaust valve of the plurality of exhaust valves isoperatively connected to the electric actuator via the tie bar.

In some embodiments of the present technology, each exhaust valve of theplurality of exhaust valves has a blade and a shaft connected to theblade. The shaft of each exhaust valve of the plurality of exhaustvalves is connected to the tie bar.

In some embodiments of the present technology, a plurality of vibrationabsorbing mounts connects the shafts of the plurality of exhaust valvesto the tie bar.

According to another aspect of the present technology, there is provideda two-stroke internal combustion engine having an engine block. Theengine block defines at least one cylinder; at least one exhaust passagecommunicating with the at least one cylinder; and at least one exhaustvalve passage communicating with the at least one exhaust passage. Theengine also has at least one piston disposed in the at least onecylinder; and the exhaust valve assembly of any one of the above aspectand embodiments connected to the engine block. The at least one exhaustvalve is disposed at least in part in the at least on exhaust valvepassage.

In some embodiments of the present technology, the housing of theexhaust valve assembly is fastened to the engine block.

Embodiments of the present technology each have at least one of theabove-mentioned object and/or aspects, but do not necessarily have allof them. It should be understood that some aspects of the presenttechnology that have resulted from attempting to attain theabove-mentioned object may not satisfy this object and/or may satisfyother objects not specifically recited herein.

Additional and/or alternative features, aspects and advantages ofembodiments of the present technology will become apparent from thefollowing description, the accompanying drawings and the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present technology, as well as otheraspects and further features thereof, reference is made to the followingdescription which is to be used in conjunction with the accompanyingdrawings, where:

FIG. 1A is a perspective view taken from a rear, left side of componentsof a two-stroke internal combustion engine for a marine outboard engine;

FIG. 1B is a top plan view of the components of the two-stroke internalcombustion engine of FIG. 1A;

FIG. 2 is a partial cross-sectional view of the engine of FIG. 1A takenthrough line 2-2 of FIG. 1B;

FIG. 3 is a partial cross-sectional view of a cylinder block and pistonof the engine of FIG. 1A taken through a horizontal plane passingthrough a center of a cylinder of the cylinder block;

FIG. 4A is the cross-sectional view of FIG. 3 with the piston removedand with a reciprocating exhaust valve shown in a retracted position;

FIG. 4B is a close-up of a region of FIG. 4A near an end of the exhaustvalve;

FIG. 5 is the cross-sectional view of FIG. 3 with the piston removed andwith the reciprocating exhaust valve shown in an intermediate position;

FIG. 6A is the cross-sectional view of FIG. 3 with the piston removedand with the reciprocating exhaust valve shown in an actuated position;

FIG. 6B is a close-up of a region of FIG. 6A near an end of the exhaustvalve;

FIG. 7 is a close-up view taken from a shaft end of the exhaust valve ofFIG. 4A showing a clearance between the exhaust valve and walls of anexhaust valve passage;

FIG. 8 is an elevation view of a side of an exhaust valve assembly ofthe engine of FIG. 1A;

FIG. 9 is an elevation view of an opposite side of the exhaust valveassembly of FIG. 8;

FIG. 10 is an elevation view of an end of the exhaust valve assembly ofFIG. 8;

FIG. 11 is an elevation view of an opposite, engine facing, side of theexhaust valve assembly of FIG. 8;

FIG. 12 is a bottom plan view of the exhaust valve assembly of FIG. 8;

FIG. 13 is an exploded view of the exhaust valve assembly of FIG. 8;

FIG. 14 is a cross-section view of the exhaust valve assembly of FIG. 8taken through line 14-14 of FIG. 11 with the exhaust valves in theretracted position;

FIG. 15 is a cross-section view of the exhaust valve assembly of FIG. 8taken through line 14-14 of FIG. 11 with the exhaust valves in theactuated position;

FIG. 16 is a partially exploded view of an electric actuator and of acover of a housing of the exhaust valve assembly of FIG. 8;

FIG. 17 is a cross-sectional view of the components of FIG. 16 takenthrough line 17-17 of FIG. 9;

FIG. 18 is a front, left side perspective view of one of the exhaustvalves of the engine of FIG. 1A;

FIG. 19 is a front elevation view of the exhaust valve of FIG. 18;

FIG. 20 is a perspective view taken from a rear, right side of theexhaust valve of FIG. 18;

FIG. 21 is a rear elevation view of the exhaust valve of FIG. 18;

FIG. 22 is a left side elevation view of the exhaust valve of FIG. 18;

FIG. 23 is a top plan view of the exhaust valve of FIG. 18;

FIG. 24 is a bottom plan view of the exhaust valve of FIG. 18;

FIG. 25 is a cross-sectional view of the exhaust valve of FIG. 18 takenthrough line 25-25 of FIG. 21 with walls of the exhaust valve passageshown in dotted lines;

FIG. 26 is a cross-sectional view of the exhaust valve of FIG. 18 takenthrough line 26-26 of FIG. 21;

FIG. 27 is a cross-sectional view of the exhaust valve of FIG. 18 takenthrough line 27-27 of FIG. 21;

FIG. 28 is a schematic illustration of an exhaust valve system of theengine of FIG. 1A;

FIG. 29 is a logic diagram illustrating a method for cleaning theexhaust valves of the exhaust valve system of FIG. 28 when the exhaustvalves fail to move to an open position;

FIG. 30 is a logic diagram illustrating a method for cleaning theexhaust valves of the exhaust valve system of FIG. 28 when the exhaustvalves fail to move to a closed position; and

FIG. 31 is a logic diagram illustrating a fault operation mode of themethods of FIGS. 29 and 30.

DETAILED DESCRIPTION

The present technology will be described with reference to a two-stroke,direct injection, internal combustion engine having a verticallyoriented crankshaft for use in a marine outboard engine. However, it iscontemplated that the present technology could be used in other types oftwo-stroke internal combustion engines such as those havinglongitudinally or laterally oriented crankshaft, and those havingsemi-direct injection or being carbureted.

With reference to FIGS. 1A, 1B and 2, a two-stroke internal combustionengine 10 has an engine block 12 to which are connected three directfuel injectors 14, three spark plugs 16 and an exhaust valve assembly100. The engine block 12 has a crankcase 18, a cylinder block 20 and acylinder head 22. The cylinder block 20 is disposed between thecrankcase 18 and the cylinder head 22. The fuel injectors 14 and thespark plugs 16 are connected to the cylinder head 22. The exhaust valveassembly 100 is connected to the cylinder block 20 as will be describedin greater detail below. It is contemplated that the exhaust valveassembly 100 could additionally or alternatively be connected to thecylinder head 22. As can be seen in FIG. 2, the exhaust valve assembly100 has a housing 102, an exhaust valve actuator in the form of anelectric actuator 104 housed in the housing 102 and three reciprocatingexhaust valves 106 operatively connected to the electric actuator 104,as will be described in greater detail below.

A crankshaft 24 is rotationally supported in the crankcase 18. An upperend of the crankshaft 24 extends from a top of the crankcase 18, asshown in FIGS. 1A and 1B, to be connected to a flywheel and magnetoassembly (not shown). A lower end of the crankshaft 24 extends from abottom of the crankcase 18 to be connected to a driveshaft (not shown)of the marine outboard engine.

The cylinder block 20 defines three cylinders 26 (FIG. 2), which will bedescribed in more detail below. Three pistons 28 (one of which ispartially shown in FIG. 3) are received in the three cylinders 26 (i.e.one piston 28 per cylinder 26). It is contemplated that the cylinderblock 20 could define only one cylinder 26, two cylinders 26 or morethan three cylinders 26, in which case the engine 10 would have acorresponding number of fuel injectors 14, spark plugs 16, exhaustvalves 106 and pistons 28.

The pistons 28 are connected to the crankshaft 24 by connecting rods(not shown). During operation of the engine 10, combustion of fuel-airmixture in the cylinders 26 causes the pistons 28 to turn the crankshaft24, and the connections of the pistons 28 to the crankshaft 24 cause thepistons 28 to reciprocate inside their respective cylinders 26.

The engine 10 has many other components which are not essential to theunderstanding of the present technology. As such these other componentswill not be described herein but would be known to a person skilled inthe art of two-stroke internal combustion engines.

With reference to FIGS. 2 and 3, one of the cylinders 26 and associatedfeatures will be described in more detail. The cylinder 26 defines acylinder axis 30 along which the piston 28 reciprocates. The cylinder 26defines four intake ports 32 (two of which are shown in FIG. 3) throughwhich air can enter the cylinder 26. The cylinder 26 also defines anexhaust port 34 through which exhaust gases can leave the cylinder 26. Acylinder liner 36 is provided in the cylinder 26. The cylinder liner 36defines ports corresponding to the ports 32, 34. As best seen in FIG. 2,the cylinder block 20 defines transfer passages 38 that fluidlycommunicate the intake ports 32 with the volume defined by the crankcase18 to permit the transfer of air from the crankcase 18 to the cylinder26. As best seen in FIG. 3, the cylinder block 20 defines an exhaustpassage 40 that extends from the exhaust port 34 and fluidlycommunicates the cylinder 26 with an exhaust system (not shown) of theengine 10. As can also be seen in FIG. 3, the cylinder block 20 alsodefines an exhaust valve passage 42 that communicates with and extendsat an angle to the exhaust passage 40. As can be seen in FIGS. 4A to 7,the exhaust valve passage 42 receives one of the exhaust valves 106 ofthe exhaust valve assembly 100 therein. The exhaust valve passage 42 hasa wall 44 and a wall 46 that are connected to each other at their endsby two arcuate walls 48 (one of which is shown in FIG. 7). The wall 44is closer to the cylinder head 22 in the direction defined by thecylinder axis 30. The exhaust valve passage 42 also has a cylindricalportion 50.

The other two cylinders 26 are identical and have corresponding transferpassages 38, exhaust passages 40 and exhaust valve passages 42. Wherevisible in FIG. 2, the corresponding features of the other two cylinders26 have been labeled with the same reference numerals.

Each reciprocating exhaust valve 106 has a shaft 108 and a blade 110connected to the shaft 108. As can be seen in FIG. 2, the shafts 108 ofthe exhaust valves 106 are operatively connected to the electricactuator 104. The shafts 108 extend in the cylindrical portions 50 oftheir corresponding exhaust valve passages 42 as can be seen in FIGS. 4Ato 7 and 25 for one of the exhaust valves 106. The blades 110 arereceived between the walls 44, 46 of their corresponding exhaust valvepassages 42 as can also be seen in FIGS. 4A to 7 and 25 for one of theexhaust valves 106. The electric actuator 104 selectively slides theexhaust valves 106 inside their respective exhaust valve passages 42between various positions along their respective reciprocation axes 112(FIG. 14). Each reciprocation axis 112 is defined by the shaft 108 ofthe corresponding exhaust valve 106. In the present embodiment, all ofthe exhaust valves 106 are moved simultaneously by the electric actuator104. In the present embodiment, each exhaust valve 106 has a retractedposition (also referred to as an open position, FIGS. 4A, 4B, 14), anintermediate position (FIG. 5), and an actuated position (also referredto as a closed position, FIGS. 6A, 6B, 8, 9, 12, 15). With reference toFIGS. 4A and 4B, in the retracted position, the blade 110 of the exhaustvalve 106 is almost completely inside its corresponding exhaust valvepassage 42 so as not to obstruct the flow of exhaust gases through theexhaust passage 40. The retracted position of the exhaust valve 106 isthe position at which the exhaust port 34 opens earliest in the enginecycle as the piston 28 travels away from the cylinder head 22 and,correspondingly, at which the piston 28 takes the longest to completelyclose the exhaust port 34 as it travels toward the cylinder head 22.With reference to FIGS. 6A and 6B, in the actuated position, the blade110 of the exhaust valve 106 extends partially out of its correspondingexhaust valve passage 42 so as to partially obstruct the flow of exhaustgases through the exhaust passage 40. The actuated position of theexhaust valve 106 is the position at which the exhaust port 34 openslatest as the piston 28 travels away from the cylinder head 22 and,correspondingly, at which the piston 28 takes the shortest to completelyclose the exhaust port 34 as it travels toward the cylinder head 22since the exhaust port 34 is already effectively partially closed by theblade 110 of the exhaust valve 106. The intermediate position of theexhaust valve 106 shown in FIG. 5 is, as its name suggest, a positionintermediate the retracted and actuated positions. In the intermediateposition, the blade 110 of the exhaust valve 106 partially obstructs theflow of exhaust gases through the exhaust passage 40, but less than inthe actuated position, so as to be more exposed to the hot exhaust gasesthan in the retracted position while not affect the port timing of theengine 10. It is contemplated that the exhaust valve 106 could havemultiple intermediate positions, each providing a different degree ofobstruction of the exhaust passage 40.

Turning now to FIGS. 8 to 17, the exhaust valve assembly 100 will bedescribed in more detail. As previously described, the exhaust valveassembly 100 includes a housing 102, an electric actuator 104 and threereciprocating exhaust valves 106.

The housing 102 includes a housing body 114, a cover 116 and a baseplate 118. As can be seen, the housing body 114 is between the cover 116and the base plate 118, and the base plate 118 is between the housingbody 114 and the blades 110 of the exhaust valves 106. When the exhaustvalve assembly 100 is mounted to the cylinder block 20, the base plate118 is disposed between the housing body 114 and the cylinder block 20.

The housing body 114 has a larger central section to receive theelectric actuator 104 therein. The central section of the housing body114 defines an aperture that is closed by the cover 116. The cover 116is fastened to the housing body 114 by six bolts 120. A sealing member122 is disposed between the housing body 114 and the base plate 118.Another sealing member 124 is disposed between the base plate 118 andthe cylinder block 20. Four bolts 126 extend through apertures definedthe housing body 114, the base plate 118 and the sealing members 122,124 and are threaded into four threaded apertures (not shown) defined inthe cylinder block 20. As a result, the exhaust valve assembly 100 isfastened to the cylinder block 20. In order to help ensure that theexhaust valve assembly 100 is properly oriented and precisely positionedon the cylinder block 20, two pins 128 extend from two corners of thebase plate 118 on a same side of the base plate 118. The pins 128 arereceived in two corresponding apertures (not shown) in the cylinderblock 20. The two pins 128 extend through apertures defined in twocorners of the housing body 114, the base plate 118 and the sealingmembers 122, 124.

With reference to FIGS. 16 and 17, the electric actuator 104 will bedescribed in more detail. The electric actuator 104 includes an electricmotor 130, a lead screw 132 and a gear box 134. The electric motor 130and the lead screw 132 are disposed side-by-side and are connected tothe gear box 134. The electric motor 130 is powered by a battery (notshown) charged by the magneto.

The electric actuator 104 is connected by a vibration absorbing mount136 to an inner side of the cover 116 of the housing 102. Vibrationabsorbing mount 136 includes an elastomeric ring 138, a retaining ring140 and four screws 142. The gear box 134 has a peripheral lip 144 thatis received in an inner channel 146 of the elastomeric ring 138. As canbe seen in FIG. 17, the elastomeric ring 138 is held between the innerside of the cover 116 and the retaining ring 140. The retaining ring 140is fastened to the cover 116 by the screws 142. As a result, the gearbox 134, and therefore the electrical actuator 104, is connected tocover 116 is such a way that the transmission of vibrations from thehousing 102 to the electrical actuator 104 is reduced by the vibrationabsorbing mount 136. When the cover 116 with the electric actuator 104attached to it is fastened to the housing body 114, the electricactuator 104 is disposed inside the volume defined by the housing body114, the cover 116 and the base plate 118 as can be seen in FIGS. 14 and15.

The wires 148 supplying power to the electric motor 130 extend from theelectric motor 130, then between the gear box 134 and the inside of thecover 116, then through an aperture 150 (FIG. 13) in the cover 116 andconnect to a connector 152. The connector 152 is connected to acontroller 262 (FIG. 29). A grommet 154 is disposed around the portionof the wires 148 extending through the aperture 150.

With reference to FIG. 17, the electric motor 130 has an output shaft156 rotationally supported in a motor housing 158. A rotor and a stator(not shown) are provided inside the motor housing 158. The rotor isconnected to the output shaft 156. As can be seen, the output shaft 156of the electric motor 130 and the lead screw 132 are parallel to eachother.

The gear box 134 includes an input gear 160, a double gear 162 mountedon a shaft 164, and an output gear 166. The double gear 162 includes amajor gear 168 and a minor gear 170 that are concentric and integral.The input gear 160 is mounted to and driven by the end of the outputshaft 156 of the electric motor 130 that extends inside the gear box134. The input gear 160 engages the major gear 168 to drive the doublegear 162. The minor gear 170 of the double gear 162 drives the outputgear 166. The output gear 166 is mounted to and drives an end of thelead screw 132 that extends inside the gear box 134.

As can be seen in FIG. 17, the lead screw 132 is rotationally supportedin the gear box 134 by a bearing 172. The lead screw 132 engages aplunger 174 having internal threads. The lead screw 132 and the plunger174 partially extend inside a lead screw housing 176. The plunger 174abuts the walls of the lead screw housing 176, which prevents theplunger 174 from rotating about a rotation axis of the lead screw 132.When the electric motor 130 drives the lead screw 132 via the gear box134, the plunger 174 moves linearly along the lead screw 132. Thedirection of movement of the plunger 174 depends on the direction ofrotation of the lead screw 132. The threads of the lead screw 132 aredesigned such that the lead screw 132 is self locking, meaning that whenthe electric motor 130 stops, the plunger 174 cannot move along the leadscrew 132 as a result of forces pushing or pulling on the plunger 174. Amagnet 264 is mounted to the side of the plunger 174 and moves along thelead screw 132 with the plunger 174. A valve position sensor 266 ismounted to the motor housing 158 for determining a position of theexhaust valves 106. The valve position sensor 266 senses a position ofthe magnet 264 and communicates this position to the controller 262. Asthere is a directed relationship between the position of the plunger 174(and therefore the magnet 264) and the position of the exhaust valves106, the signal from the valve position sensor 266 is indicative of theposition of the exhaust valves 106 and can be used to determine theposition of the exhaust valves 106. It is contemplated that other typesof valve position sensors could be used. For example, a valve positionsensor could sense the position of one of the exhaust valves 106directly.

The plunger 174 defines a slot 178 (FIG. 17). As can be seen in FIG. 14,the head of a coupler 180 is received in the slot 178 such that thecoupler 180 moves linearly with the plunger 174. The coupler 180 hasexternal threads that thread into an aperture of a tie bar 182. The tiebar 182 is disposed in the volume defined by the housing 102. The tiebar 182 is disposed between the electric actuator 104 and the base plate118. Two of the bolts 126 extend through apertures in the tie bar 182.

The tie bar 182 operatively connects the exhaust valves 106 to theelectric actuator 104. More specifically, as can be seen in FIG. 14, theshafts 108 of the exhaust valves 106 extend through the base plate 118inside the volume defined by the housing 102, and the ends of the shafts108 connect to the tie bar 182. For each exhaust valve 106, the housing102 includes a seal 184 disposed between the shaft 108 of the exhaustvalve 106 and the base plate 118 to prevent exhaust gases from enteringthe housing 102. For each exhaust valve 106, a vibration absorbing mount186 connects the shaft 108 of the exhaust valve 106 to the tie bar 182.The vibration absorbing mounts 186 reduce the transmission of vibrationsfrom the exhaust valves 106 to the electric actuator 104. It is alsocontemplated that a vibration absorbing mount could be provided betweenthe coupler 180 and the tie bar 182 and/or between the coupler 180 andthe plunger 174.

When the electric motor 130 turns in one direction, the lead screw 132moves the plunger 174 toward the base plate 118. As a result, the tiebar 182 moves toward the base plate 118, which moves the exhaust valves106 simultaneously such that the blades 110 of the exhaust valves 106move linearly away from the base plate 118 up to the actuated positionof the exhaust valves 106 shown in FIG. 15. When the electric motor 130turns in the other direction direction, the lead screw 132 moves theplunger 174 away from the base plate 118. As a result, the tie bar 182moves away from the base plate 118, which moves the exhaust valves 106simultaneously such that the blades 110 of the exhaust valves 106 movelinearly toward the base plate 118 up to the retracted position of theexhaust valves 106 shown in FIG. 14.

The exhaust valve assembly 100 also have three pairs of exhaust valvepassage fillers 188, one per exhaust valve 106, connected to the baseplate 118. In the present embodiment, the exhaust valve passage fillers188 are integral with the base plate 118, but it is contemplated thatthey could be connected in other ways. As can be seen in FIGS. 14 and15, for each exhaust valve 106, the shaft 108 of the exhaust valve 106extends between its two corresponding exhaust valve passage fillers 188,and the corresponding exhaust valve passage fillers 188 are disposedbetween the base plate 118 and the blade 110 of the exhaust valve 106.As can be seen in FIG. 14, when the exhaust valves 106 are in theirretracted positions, the exhaust valve passage fillers 188 generallyfollow a contour of their corresponding exhaust valves 106. As theirname suggests, the exhaust valve passage fillers 188 fill portions ofthe exhaust valve passages 42. More specifically, the exhaust valvepassage fillers 188 fill the portions of the exhaust valve passages 42located between the blades 110 of the exhaust valves 106 and the baseplate 118 as can be seen in FIG. 2. The exhaust valve passage fillers188 help reduce potential carbon build up in the exhaust valve passages42 between the blades 110 of the exhaust valves 106 and the base plate118.

Turning now to FIGS. 18 to 27, additional details of the exhaust valves106 will be described. As all three exhaust valves 106 are identical,these details will be described with respect to only one exhaust valve106. Also, for simplicity, the exhaust valve 106 will be described withrespect to a frame of reference of the exhaust valve 106, not the frameof reference of the engine 10. In the frame of reference of the exhaustvalve 106, the side of the exhaust valve 106 shown in FIG. 21 is a rearof the exhaust valve 106 and, in FIG. 21, the right side of the exhaustvalve 106 is on the right and the left side of the exhaust valve 106 ison the left. Also, in the frame of reference of the exhaust valve 106,the top of the exhaust valve 106 corresponds to the free end of shaft108, the bottom of the exhaust valve 106 corresponds to the free end ofthe blade 110, and the reciprocation axis 112 extends vertically. In theframe of reference of the engine 10, the reciprocation axis 112 extendshorizontally. In the frame of reference of the exhaust valve 106, thereciprocation axis 112 defines a longitudinal direction, and the lateraldirection is perpendicular to the longitudinal direction in the planedefined by the page of FIG. 19. Height is measured in the longitudinaldirection. Width is measure in the lateral direction. Thickness ismeasured in a direction perpendicular to the longitudinal and lateraldirections (i.e. in a direction normal to the plane defined by the pageof FIG. 19).

In the present embodiment, the shaft 108 and the blade 110 of theexhaust valve 106 are integral and are made of a relatively low thermalconductivity material. One example of such a material is stainlesssteel. Other materials are contemplated.

The shaft 108 has an upper portion 200, a middle portion 202 and a lowerportion 204. With reference to FIG. 19, the upper portion 200 iscylindrical and has a diameter D1. The upper portion 200 is the portionof the shaft 108 that is received in the vibration absorbing mount 186to connect the shaft 108 to the tie bar 182. The middle portion 202 iscylindrical and has a diameter D2 that is larger than the diameter D1.The middle portion 202 is the portion of the shaft 108 that passesthrough the base plate 118 and the seal 184. The lower portion 204defines a stopper 206 and a neck 208. The stopper 206 has a diameter D3that is larger than the diameters D1 and D2. The neck 208 has agenerally rectangular cross-section. The neck 208 disposed between thestopper 206 and the upper end 210 of the blade 110. The neck 208connects the shaft 108 to the upper end 210 of the blade 110.

As seen in FIG. 25, the stopper 206 is received in the cylindricalportion 50 of the exhaust valve passage 42. The diameter D3 is sized soas to be in sliding fit with the cylindrical portion 50 of the exhaustvalve passage 42. In one embodiment, a clearance C1 between the stopper206 and the walls of the cylinder block 20 defining the cylindricalportion 50 of the exhaust valve passage 42 has a nominal value of 0.1mm. As best seen in FIG. 7, this clearance C1 is less than a minimumclearance between the blade 110 and the walls of the cylinder block 20defining the exhaust valve passage 42. This minimum clearance is aclearance C2 between a front face 212 of the blade 110 and the wall 44of the exhaust valve passage 42. In one embodiment, the clearance C2 hasa nominal value of 0.28 mm which is almost three times as large as theclearance C1 of 0.1 mm. The sliding fit between the stopper 206 and thewalls of the cylinder block 20 defining the cylindrical portion 50 allowthe stopper 206 to accurately guide the blade 110 as the exhaust valve106 is reciprocated along the reciprocation axis 112 by the electricactuator 104.

The stopper 206 has stopper surfaces 214 facing toward the lower end 216of the blade 110. As can be seen in FIG. 25, the exhaust valve passage42 defines step 218. In order to prevent the blade of the exhaust valve106 from extending too far into the exhaust passage 40 when it is movedto the actuated position and in order to support the exhaust valve 106when in the actuated position, the stopper surfaces 214 abut the steps218. The stopper 206 also has a stopper surface 219 facing toward theupper end of the shaft 108. In order to prevent the blade 110 of theexhaust valve 106 to extend too far out of the exhaust passage 40 whenit is moved to the retracted position, the stopper surface 219 abuts theexhaust valve passage fillers 188 as can be seen in FIG. 14.

As described above, the blade 110 of the exhaust valve 106 has an upperend 210, a lower end 216 and a front face 212. The exhaust valve 106also has a rear face 220. The faces 212, 220 extend between the ends210, 216. When the exhaust valve 106 is disposed in the exhaust valvepassage 42, the front face 212 faces the wall 44 and the rear face 220faces the wall 46 as can be seen in FIG. 25. In order to ensure that theexhaust valve 106 is inserted in the exhaust valve passage 42 in thisorientation, the blade 110 has a poka yoke in the form of a protrusion222 extending from its left side. The exhaust valve passage 42 has acorresponding slot (not shown) on only one of its side, thus ensuringthat the blade 110 can only be inserted in one orientation.

As can be seen, a majority of the front face 212 is flat. The rear face220 has various features that will be described in more detail below.The lower end 216 of the blade 110 has an arcuate edge 224 extendingalong a majority of its width. The lower end 216 also defines twonotches 226 at its lateral ends. The arcuate edge 224 is angled so thatit is generally parallel to the cylinder axis 30 when the exhaust valve106 is in the exhaust valve passage 42. The radius of curvature of thearcuate edge 224 is selected so that the arcuate edge 224 closelyfollows the curvature of the cylinder liner 36 when the exhaust valve106 is in the actuated position. The notches 226 ensure the arcuate edge224 can be moved into the exhaust port 34 when the exhaust valve 106 isin the actuated position without having the blade 110 contact thecylinder liner 36. As can be seen in FIG. 19, the upper end 210 of theblade 110 has two arcuate edges 228 and the shaft 108 is connectedbetween the two arcuate edges 228. The radius of curvature of thearcuate edges 228 is greater than the radius of curvature of the arcuateedge 224.

The blade 110 has a central portion 230 disposed laterally between twoside portions 232. As would be understood from FIG. 22, a cross-sectionof each of the side portions 232 taken through a plane extending in thelateral direction and being normal to the reciprocation axis 112 issemi-circular. With reference to FIG. 19, it can be seen that a width W1of the central portion 230 is greater than half of a width W2 of theblade 110. It can also be seen that the width W1 of the central portion230 is greater that a width W3 of each side portion 232, and greaterthan a sum of the widths W3 of the side portions 232.

With reference to the cross-section of FIG. 25, the blade 110 has alower portion 234 adjacent its lower end 216, an upper portion 236adjacent its upper end 210, and a mid-portion 237 longitudinally betweenthe lower and upper portions 234, 236. These portions 234, 236, 237 aregenerally arcuate (i.e. following the upper and/or lower curvatures ofthe blade 110) and extend the width of the blade 110. The portions ofthe central portion 230 located in the upper portion 236 adjacent to thearcuate edges 228 are referred to herein as sub-portions 238. Theportion of the central portion 230 located in the mid-portion 237 isreferred to herein as the central mid-portion 240.

As can be seen in FIG. 25, the part of the central portion 230 in thelower portion 234 has a thickness T1, the central mid-portion 240 has athickness T2, the sub-portions 238 have a thickness T3, and the sideportions 232 have a thickness T4. It can be seen that the thickness T2is greater than the thickness T1 and greater than the thickness T3. Thethickness T1 is slightly greater than the thickness T3. The thickness T4is greater than the thickness T1. By comparing FIGS. 25 and 27, it canalso be seen that the portion of the central portion 230 disposedlaterally between the two sub-portions 238 has a thickness T5 which isgreater than the thickness T3 of the sub-portions 238.

The thin portions of the blade 110 (i.e. portions having thicknesses T1and T3), under certain operating conditions of the engine 10, are morelikely to heat up above the carbon burn-off temperature thereby burningoff these components than the blades of other existing exhaust valves.Other geometric characteristics of the blade 110 also contribute to theheating of the blade 110.

The thicker portions of the blade 110 (i.e. portions having thicknessesT2, T4 and T5) contributed to the rigidity of the blade 110. To furtherenhance its rigidity, the blade 110 is provided with a reinforcingstructure having three ribs 242 on its rear face 220. It is contemplatedthat there could be more or less than three ribs 242 or that thereinforcing structure could taken another form. The ribs 242 aredisposed laterally between the sub-portions 238 and are aligned with theshaft 108. To rigidify the sub-portions 238, each side portion 232defines a flange 244 adjacent to the upper end 210. The flanges 244 areconnected to and extend perpendicular to their respective sub-portions238.

With reference to FIGS. 23 and 24, the blade 110 defines two channels250 along its rear face 220 that extend longitudinally. The channels 250are on opposite sides of the reciprocation axis 112 and are adjacent totheir corresponding side portions 232. Each channel 250 is defined onone side by its corresponding side portion 232 and on the other side bythe reinforcing structure having the ribs 242.

The channels 250 and the wall 46 define a valve passage 252 that fluidlycommunicates with the exhaust passage 40. The valve passage 252 extendsthe width of the central portion 230 in the lower portion 234 of theblade 110. As such the passage 252 has a width W4 (FIG. 24) that isgreater than half of the width W2 of the blade 110. In otherembodiments, the width W4 of the passage 252 is greater than at least athird of the width W2 of the blade 110. A maximum thickness T6 (FIG. 24)of the passage 252 is at least one third of the diameter D3 of thestopper 206.

The passage 252 permits the flow of exhaust gases along the rear face220 between the ends 210, 216 of the blade 110 and into and out of thespace of the exhaust valve passage 42 between the upper end 210 of theblade 110 and the exhaust valve passage fillers 188. Due to itsrelatively large size, a substantial flow of exhaust gases along therear face 220 of the blade 110 is permitted which permits the exhaustgases, under certain operating conditions of the engine 10, to heat theblade 110 above the carbon burn-off temperature of exhaust componentsthat may have accumulated on the blade 110. Also, the size of thepassage 252 does not promote the compaction of the exhaust gascomponents between the blade 110 and the wall 46 of the exhaust valvepassage 42 and permits these components to fall into the exhaust passage40 as the exhaust valve 106 reciprocates. Finally, when the relativelythin upper portion 236 of the blade 110 moves to the retracted position,it can make contact with any exhaust components that may have built upon the ends of the exhaust valve passage fillers 188, thus breaking upthese components which then fall through the passage 252 into theexhaust passage 40.

Turning now to FIG. 28, the controller 262, together with the actuator104, the exhaust valves 106, the valve position sensor 266 and othercomponents of the exhaust valve assembly 100 form an exhaust valvesystem 260. The controller 262 receives signals from various sensors.These include a throttle position sensor (not shown), the valve positionsensor 266, and other sensors on the engine 10, such as an engine speedsensor (not shown). Additional sensors could also send signals to thecontroller 262. Based on these signals, the controller 262 communicateswith the actuator 104 for controlling it. The actuator 104 then attemptsto move the exhaust valves 106 to the desired position in response tothe signals received from the controller 262. In the present embodiment,the controller 262 also sends signals to the engine 10 to control thefuel injection and ignition and to a throttle valve actuator (not shown)to control the air intake to the engine 10 in order to control engineoperation. It is contemplated that in other embodiments, a separatecontroller communicating with the engine and the controller 262 couldcontrol the operation of the engine 10. It is contemplated that thefunctions of the controller 262 could be split between multiple controlunits.

Turning now to FIGS. 29 to 31, methods 300, 400 for cleaning the exhaustvalves 106 of the exhaust valve system 260 described above will bedescribed. It is contemplated that the methods 300, 400, or at leastsome aspects of these methods could be used with an exhaust valve systemhaving a different type of exhaust valves and/or a different type ofactuator. The controller 302 is programmed to carry out the steps of themethods 300 and 400. In the present embodiment, the actuator 104 movesall three exhaust valves 106 together. As such, if any one of theexhaust valves 106 cannot reach a desired one of an open or closedposition because this exhaust valve 106 needs to be cleaned, then allthree exhaust valves 106 will not reach this position and all threeexhaust valves 106 will be cleaned according to the method 300 or 400.The term “cleaning” refers to the removal of exhaust components thathave built up on the exhaust valves 106, and more specifically on theblade 110 of the exhaust valve 106. This build-up of exhaust componentscan get caught between the blade 110 of the exhaust valve 106 and thesurrounding components, thus preventing the exhaust valves 106 to reachthe open or closed positions. As all three exhaust valves 106 movetogether, the methods 300, 400 will be described with respect to asingle exhaust valve 106. It should be understood that when referring toa condition of “the exhaust valve 106”, this condition may only need tobe met by one of the three exhaust valves 106. For example, when withreference to step 308 below it is described that “the exhaust valve 106is stuck”, it should be understood that only one of the exhaust valves106 needs to be stuck for the described condition to be met because ifone exhaust valve 106 is stuck, then the other two exhaust valves 106are in the same position as this exhaust valve 106.

In the methods 300 and 400, the position of the exhaust valve 106 isdescribed in terms of percentage, with 100% being the fully openedposition (i.e. the position at which the exhaust valve 106 is mostretracted inside the corresponding exhaust valve passage 42) and 0%being the fully closed position (i.e. the position at which the exhaustvalve 106 is most extended inside the exhaust passage 40). In thepresent embodiment, the 0% and 100% positions are calibrated at thefactory and the corresponding readings obtained from the valve positionsensor 266 are stored in the controller 262. It is contemplated that the0% and 100% positions could be re-calibrated after maintenance of theexhaust valve assembly 100 or replacement of parts of the exhaust valveassembly 100. In the present embodiment, the intermediate positionreferred to in the methods 300 and 400 is at 50% (i.e. halfway betweenthe fully open and fully closed positions). It is contemplated that theintermediate position could be another position of the exhaust valve 106where the blade 110 of the exhaust valve 106 is more exposed to the hotexhaust gases than in the retracted position. It is contemplated thatthe position of the exhaust valve 106 could be expressed differently.For example, the position could be expressed in terms of a distance fromone of the open and closed positions. In another example, the fully openposition could correspond to 0% and the fully closed position couldcorrespond to 100%. In the present embodiment, the engine 10 normallyoperates with the exhaust valve 106 in either the closed or openpositions, with the intermediate position used solely for cleaning theexhaust valve 106. It is contemplated that the engine 10 could operatenormally in closed, open and one or more intermediate positions.

The method 300 is used when the exhaust valve 106 is in the closedposition and the controller 262 determines that based on the throttlerequest from the user and the operating conditions of the engine 10 theexhaust valve 106 should be moved to the open position. The method 400is used when the exhaust valve 106 is in the open position and thecontroller 262 determines that based on the throttle request form theuser and the operating conditions of the engine 10 the exhaust valveshould be moved to the closed position. The methods 300, 400 are used toattempt to clean the exhaust valve 106 in the event that the actuator104 is unable to move the exhaust valve 106 to the desired one of theopen and closed position in an attempt to permit the actuator 104 toeventually move the exhaust valve to the desired one of the openposition and the closed position. The operating condition of then engine10 is determined by the controller 262 based on the signals receivedfrom the various sensors that communicate with the controller 262, someof which have been described above.

Turning now to FIG. 29, the method 300 for cleaning the exhaust valve106 will be described. At step 302, the controller 262 sets a counter Xto zero. This step is only done once when the engine 10 is firststarted. The counter X will not be reset to zero until the engine 10 isturned off, then turned on again. From step 302, the controller 262proceeds to step 304. As would be understood from the above, should themethod 300 be carried out more than once after the engine 10 hasstarted, the controller 262 will begin the method 300 at step 304.

At step 304, the controller 262 determines, based on the operatingcondition of the engine 10, if the exhaust valve 106 should be in theopen position. If the desired position is the open position, then thecontroller 262 proceeds to step 306 to initiate the remainder of themethod 300.

At step 306, the controller 262 sends a signal to the actuator 104 tomove the exhaust valve 106 to the open position (100% position), inresponse to which the controller 104 attempts to move the exhaust valve106 to this position. Then at step 308, based on the signal receivedfrom the valve position sensor 266, the controller 262 determines if theexhaust valve 106 has failed to reach the open position. To do this, thecontroller 262 compares the position sensed by the valve position sensor266 to the desired valve position, which in this case is the 100% openposition. Even if the 100% open position is not reached, if the exhaustvalve 106 has reached a position that is greater than 92%, then thecontroller 262 determines that the exhaust valve 106 is sufficientlyclose to the desired open position. As a result, the system is satisfied(step 336), no exhaust valve cleaning is required, and the controller262 will reinitiate method 300 the next time the exhaust valve 106 is tobe moved from the closed position to the open position. It iscontemplated that the percentage used at step 308 could be more or lessthan 92%. If at step 308 the controller 262 determines that the exhaustvalve 106 has failed to reach the desired open position (i.e. theposition of the exhaust valve 106 is not greater than 92%), then thecontroller 262 proceeds to step 310.

At step 310, the controller 262 determines if the exhaust valve 106 hasmoved by a distance that is more than 5%. To do this, the controller 262compares the position of the exhaust valve 106 sensed by the valveposition sensor 266 before the controller 262 sent the signal to thecontroller 104 at step 306 to the position of the exhaust valve 106sensed by the valve position sensor 266 after the controller 104 hasattempted to move the exhaust valve 106 to the open position at step306. If the difference between these two positions is less than or equalto 5%, this indicates that the exhaust valve 106 is stuck. As a result,the controller 262 enters a fault operation mode 500 which will bedescribed below. If at step 310 the controller 262 determines that theexhaust valve 106 is not stuck, then the controller proceeds to step312. It is contemplated that the percentage used at step 310 could bemore or less than 5%.

At step 312, based on the signal received from the valve position sensor266, the controller 262 determines if the exhaust valve 106 has reacheda position that is greater than 70%. If not, the controller 262 proceedsto step 338. Step 338 and the subsequent steps will be described ingreater detail below. If the exhaust valve 106 has reached a positionthat is greater than 70% (but less than or equal to 92%), then thecontroller proceeds to step 314. It is contemplated that the percentageused at step 312 could be more or less than 70%.

At step 314, the controller 262 resets a counter n to zero. Then at step316, the controller 262 sends a signal to the actuator 104 to move theexhaust valve 106 to the intermediate position (50% position), inresponse to which the controller 104 moves the exhaust valve 106 to thisposition. The actuator 104 maintains the exhaust valve 106 in theintermediate position for 30 seconds. During this time, the exhaustvalve 106 is exposed to the hot exhaust gases and the blade 110 of theexhaust valve heats up, which can lead to exhaust components present onthe blade 110 to burn off or break off the blade 110, without changingthe port timing. It is contemplated that the amount of time at step 316could be more or less than 30 seconds. After 30 seconds, the controller262 proceeds to step 318. At step 318, the controller 262 sends a signalto the actuator 104 to move the exhaust valve 106 to the open position(100% position), in response to which the controller 104 reattempts tomove the exhaust valve 106 to this position. Then the controller 262proceeds to step 320. As step 320, the controller 262 determines if theexhaust valve 106 has failed again to reach the open position in thesame way in which this was determined at step 308. If at step 320 thecontroller 262 determines that the exhaust valve 262 has reached theopen position, then exhaust valve 106 is considered to have beensuccessfully cleaned and the controller 262 proceeds to step 336described above. If at step 320 the controller 262 determines that theexhaust valve 262 has failed to reach the open position again, then thecontroller 262 proceeds to step 322.

At step 322, the controller 262 increases the counter n by 1, and thenat step 324 determines if the counter n has reached 5. It iscontemplated that the value of the counter n at step 324 could be moreor less than 5. If the counter n has not reached 5 at step 324, then thecontroller 262 returns to step 316 and the following steps are repeated.The cycles of heating and moving of the exhaust valve 106 should cleanat least some of the exhaust components that have accumulated on theblade 110 of the exhaust valve 106. Also, when the actuator 104reattempts to move the exhaust valve 106 to the open position, therelatively thin upper portion 236 of the blade 110 can contact anyexhaust components that may have built up on the ends of the exhaustvalve passage fillers 188, thus breaking up these components which thenfall through the passage 252 into the exhaust passage 40. If at step 324the counter n has reached 5, then the controller 262 proceeds to step326.

At step 326, the controller 262 makes the same verification as in step312. This is done in case the exhaust valve 106 now moves to a positionthat is less than or equal to 70% due to exhaust components that mayhave broken off from the blade 110 of the exhaust valve 106 during steps316 to 320 which could have accumulated between the blade 110 and theexhaust passage fillers 188. If at step 326, the controller determinesthat the exhaust valve 106 is at a position that is less than or equalto 70%, then the controller proceeds to step 338 which will be describedbelow. If at step 326, the exhaust valve 106 is at a position greaterthan 70%, then the controller proceeds to step 328.

At step 328, the actuator 104 maintains the exhaust valve 106 in itscurrent position for 5 minutes. It is contemplated that this could bemore or less than 5 minutes. Once the 5 minutes have elapsed, at step330 the controller 262 sends a signal to the actuator 104 to move theexhaust valve 106 to the intermediate position (50% position), inresponse to which the controller 104 moves the exhaust valve 106 to thisposition. The actuator 104 maintains the exhaust valve 106 in theintermediate position for 1 second. It is contemplated that the amountof time at step 316 could be more or less than 1 second. After 1 second,the controller 262 proceeds to step 332. At step 332, the controller 262sends a signal to the actuator 104 to move the exhaust valve 106 to theopen position (100% position), in response to which the controller 104reattempts to move the exhaust valve 106 to this position. Then thecontroller 262 proceeds to step 334. As step 334, the controller 262determines if the exhaust valve 106 has failed again to reach the openposition in the same way in which this was determined at step 308. If atstep 334 the controller determines that the exhaust valve 262 has notfailed to reach the open position, then the exhaust valve 106 isconsidered to have been successfully cleaned and the controller 262proceeds to step 336 described above. If at step 334 the controllerdetermines that the exhaust valve 262 has failed to reach the openposition again, then the controller 262 returns to step 328.

If from steps 312 and 326 the controller 262 proceeds to step 338, thenat step 338 the controller 262 determines if the value of the counter Xis zero. If the value of the counter X is zero, then the controller 262proceeds to step 340 where the controller 262 triggers a position faultcode indicative that there was a problem in attempting to reach the openposition of the exhaust valve 106. This position fault code can later beread from the controller 262 during maintenance of the engine 10. Fromstep 340, the controller 262 proceeds to step 342. If the value of thecounter X is not zero at step 338, the controller 262 also proceeds tostep 342.

At step 342, the controller 262 sends a signal to the actuator 104 toreturn the exhaust valve 106 to the closed position (0% position), inresponse to which the controller 104 moves the exhaust valve 106 to thisposition. Then the controller 262 proceeds to step 344 where thedetermines if the value of the counter X is three. It is contemplatedthat the value of the counter X at step 344 could be one, two or morethan three. If at step 344 the counter X has a value of three, then thecontroller 262 determines that the open position cannot be reached andat step 352 the exhaust valve 106 is maintained in the closed positionuntil the engine 10 is turned off.

If at step 344 the counter X has not reached three, then at step 346,the counter X is increased by one. Then at step 348, the actuator 104maintains the exhaust valve 106 in the closed position until it isdetermined by the controller 262 that the engine 10 has accumulated 5minutes of operation above 4200 RPM since the valve has been moved tothe closed position at step 342, thus heating up the blade 110 of theexhaust valve 106. It is contemplated that at step 348 the time could bemore or less than 5 minutes and the engine speed could be more or lessthan 4200 RPM. From step 348, the controller 262 proceeds to step 350where the position fault code that was triggered at step 340 is clearedfrom the controller 262. From step 350, the controller 262 returns tostep 306.

Turning now to FIG. 30, the method 400 for cleaning the exhaust valve106 will be described. At step 402, the controller 262 determines, basedon the operating condition of the engine 10, if the exhaust valve 106should be in the closed position. If that exhaust valve 106 is in theopen position but the desired position is the closed position, then thecontroller 262 proceeds to step 404 to initiate the remainder of themethod 400.

At step 404, the controller 262 sends a signal to the actuator 104 tomove the exhaust valve 106 to the closed position (0% position), inresponse to which the controller 104 attempts to move the exhaust valve106 to this position. Then at step 406, based on the signal receivedfrom the valve position sensor 266, the controller 262 determines if theexhaust valve 106 has reached or failed to reach the closed position. Todo this, the controller 262 compares the position sensed by the valveposition sensor 266 to the desired valve position, which in this case isthe 0% closed position. Even if the 0% closed position is not reached,if the exhaust valve 106 has reached a position that is less than 5%,then the controller 262 determines that the exhaust valve 106 issufficiently close to the desired closed position. As a result, thesystem is satisfied (step 426), no exhaust valve cleaning is required,and the controller 262 will reinitiate method 400 the next time theexhaust valve 106 is to be moved from the open position to the closedposition. It is contemplated that the percentage used at step 308 couldbe more or less than 5%. If at step 406 the controller 262 determinesthat the exhaust valve 106 has failed to reach the desired closedposition (i.e. the position of the exhaust valve 106 is not less than5%), then the controller 262 proceeds to step 408.

At step 408, the controller 262 determines if the exhaust valve 106 hasmoved by a distance that is more than 5%. To do this, the controller 262compares the position of the exhaust valve 106 sensed by the valveposition sensor 266 before the controller 262 sent the signal to thecontroller 104 at step 404 to the position of the exhaust valve 106sensed by the valve position sensor 266 after the controller 104 hasattempted to move the exhaust valve 106 to the closed position at step404. If the difference between these two positions is less than or equalto 5%, this indicates that the exhaust valve 106 is stuck. As a result,the controller 262 enters the fault operation mode 500 which will bedescribed below. If at step 408 the controller 262 determines that theexhaust valve 106 is not stuck, then the controller proceeds to step410. It is contemplated that the percentage used at step 408 could bemore or less than 5%.

At step 410, based on the signal received from the valve position sensor266, the controller 262 determines if the exhaust valve 106 has reacheda position that is less than 30%. If not, the controller 262 enters thefault operation mode 500. If the exhaust valve 106 has reached aposition that is less than 30% (but more than or equal to 5%), then thecontroller proceeds to step 412. It is contemplated that the percentageused at step 410 could be more or less than 30%.

At step 412, the controller 262 resets a counter n to zero. Then at step414, the actuator 104 maintains the exhaust valve 106 in its currentposition for 10 seconds. It is contemplated that the time at step 414could be more or less than 10 seconds. Once the 10 seconds have elapsed,then at step 416 the controller 262 sends a signal to the actuator 104to move the exhaust valve 106 to the intermediate position (50%position), in response to which the controller 104 moves the exhaustvalve 106 to this position. The actuator 104 maintains the exhaust valve106 in the intermediate position for 1 second. It is contemplated thatthe amount of time at step 416 could be more or less than 1 second.After 1 second, the controller 262 proceeds to step 418. At step 418,the controller 262 sends a signal to the actuator 104 to move theexhaust valve 106 to the closed position (0% position), in response towhich the controller 104 reattempts to move the exhaust valve 106 tothis position. Then the controller 262 proceeds to step 420. As step420, the controller 262 determines if the exhaust valve 106 has failedagain to reach the closed position in the same way in which this wasdetermined at step 406. If at step 420 the controller 262 determinesthat the exhaust valve 262 has not failed to reach the closed position,then exhaust valve 106 is considered to have been successfully cleanedand the controller 262 proceeds to step 426 described above. If at step420 the controller 262 determines that the exhaust valve 262 has failedto reach the closed position again, then the controller 262 proceeds tostep 422.

At step 422, the controller 262 increases the counter n by 1, and thenat step 424 determines if the counter n has reached 5. It iscontemplated that the value of the counter n at step 424 could be moreor less than 5. If the counter n has not reached 5 at step 424, then thecontroller 262 returns to step 414 and the following steps are repeated.The cycles of heating and moving of the exhaust valve 106 should cleanat least some of the exhaust components that have accumulated on theblade 110 of the exhaust valve 106. If at step 424 the counter n hasreached 5, then the controller 262 enters the fault operation mode 500.

Turning now to FIG. 31, the fault operation mode 500 of the methods 300,400 will be described. Upon entering the fault operation mode 500, atstep 502 the controller 262 triggers a position fault code indicativethat there was a problem in attempting to reach the open or closedposition, as the case may be, of the exhaust valve 106. This positionfault code can later be read from the controller 262 during maintenanceof the engine 10. From step 502, the controller 262 proceeds to step 504where the controller 262 triggers a system critical fault codeindicative that the degree by which the desired open or closed positioncould not be reached is significant. This could be indicative of theexhaust valve 106 being stuck due to a large build-up of exhaustcomponents that cannot be cleaned by the method 300 or 400, as the casemay be, or could also indicate a mechanical or electrical failure in theexhaust valve system 260. This system critical fault code can later beread from the controller 262 during maintenance of the engine 10. Thenat step 506, the controller 506 sends a signal to a display gaugeassociated with the engine 10 to flash a warning light that can be seenby the user of the engine 10 to indicate that there is a fault with theexhaust valve system 260 specifically, or more generally with the engine10. It is contemplated that instead of or in addition to flashing awarning light at step 506, an audible warning sound could be emitted, orsome other feedback could be given to the user of the engine 10. Then atstep 508, the controller 262 controls the engine 10 in a limp home mode.In the limp home mode, which can also be referred to a “safe” mode, theperformance of the engine 10 is limited. This includes limiting themaximum speed of the engine 10 and/or limiting the acceleration of theengine 10. In some embodiments, the controller 262 will continue tooperate the engine 10 in the limp home mode until maintenance isperformed on the engine 10 and the system critical fault code of step504 is cleared from the controller 262 by the technician performing themaintenance. It is contemplated that the steps 502 to 508 could beperformed in any order. It is also contemplated that the fault operationmode 500 could include shutting the engine 10 down entirely.

In some embodiments, the position of the exhaust valves 106 iscontinuously monitored by the controller 262 via the valve positionsensor 266 to determine if the exhaust valves 106 drift. The exhaustvalves 106 are said to drift when their positions change without signalsto do so sent by the controller 262. This could occur due to the leadscrew 132 being worn for example, but there are other possible reasonswhy such slow, non-deliberate movement of the exhaust valves 106 couldoccur. When the controller 262 determines that the exhaust valves 106are drifting, for example that they have moved by a distance of morethan 5% from their desired position, the controller 262 sends a signalto the electric motor 130 to move the exhaust valves 106 back to theposition that the exhaust valves 106 should have. In some embodiments,should the exhaust valves 106 drift and be returned to their correctposition a certain number of times, for example five times, before achange of position of the exhaust valves 106 is requested, from theretracted position to the actuated position for example, the controller262 triggers a drift fault code indicative of drifting of the exhaustvalves 106. This drift fault code can later be read from the controller262 during maintenance of the engine 10.

As discussed above, when in the actuated position, the stopper surfaces214 of the exhaust valves 106 abut the steps 218 of the exhaust valvepassages 42, and when in the retracted position, the stopper surfaces219 of the exhaust valves 106 abut the exhaust valve passage fillers188. In order to properly keep the exhaust valves 106 in thesepositions, a certain clamping load is applied to the exhaust valves 106by the electric motor 130 of the electric actutator 104. As a result ofthe clamping load being applied, the vibration absorbing mount 136 andthe vibration absorbing mounts 186 are compressed. However, should theclamping load applied be too high, the vibration absorbing mounts 136,186 can become too compressed, thereby reducing their effectiveness atreducing the transmission of vibrations. As such, in some embodiments,the controller 262 controls the clamping load being applied by theelectric motor 130 to correspond to a desired clamping load. The desiredclamping load is a clamping load that is sufficiently high to properlykeep the exhaust valves 106 in their actuated and retracted positions,but that is not high enough to negatively affect the effectiveness ofthe vibration absorbing mounts 136, 186. It is contemplated that thedesired clamping load for the actuated position of the exhaust valves106 could be different from the desired clamping load for the retractedposition of the exhaust valves 106. As indicated above, the electricmotor 130 is powered by a battery. The voltage of the battery variesduring use as the battery charges and discharges. For a given dutycycle, the load applied by the electric motor 130 will vary depending onthe actual voltage of the battery. In order to apply the desiredclamping load, the controller 262 determines the actual voltage of thebattery and then adjusts the duty cycle used to control the electricmotor 130 accordingly. The higher the actual voltage of the battery is,the lower the duty cycle will be so as to obtain the desired clampingload regardless of the actual voltage of the battery.

Modifications and improvements to the above-described embodiments of thepresent technology may become apparent to those skilled in the art. Theforegoing description is intended to be exemplary rather than limiting.The scope of the present technology is therefore intended to be limitedsolely by the scope of the appended claims.

What is claimed is:
 1. An exhaust valve system for a two-stroke internalcombustion engine comprising: at least one exhaust valve movable betweenan open position and a closed position; an actuator operativelyconnected to the at least one exhaust valve for moving the at least oneexhaust valve between the open position and the closed position; a valveposition sensor for determining a position of the at least one exhaustvalve; a controller communicating with the actuator for controlling theactuator, the controller communicating with the valve position sensorfor receiving a signal indicative of the position of the at least oneexhaust valve, the controller being programmed for: a) controlling theactuator to attempt to move the at least one exhaust valve to a desiredone of the open position and the closed position; b) determining if theat least one exhaust valve has failed to reach the desired one of theopen position and the closed position based on the position of the atleast one exhaust valve sensed by the valve position sensor; and c)controlling the actuator to move the at least one exhaust valve to anintermediate position when the at least one exhaust valve has failed toreach the desired one of the open position and the closed position, theintermediate position of the at least one exhaust valve being betweenthe open position and the closed position.
 2. The exhaust valve systemof claim 1, wherein determining if the at least one exhaust valve hasfailed to reach the desired one of the open position and the closedposition comprises comparing the position of the at least one exhaustvalve sensed by the valve position sensor to the desired one of the openposition and the closed position.
 3. The exhaust valve system of claim2, wherein controlling the actuator to move the at least one exhaustvalve to the intermediate position comprises controlling the actuator tomove the at least one exhaust valve to the intermediate position for apredetermined amount of time; and once the at least one exhaust valvehas been in the intermediate position for the predetermined amount oftime, the controller is further programmed for: d) controlling theactuator to reattempt to move the at least one exhaust valve to thedesired one of the open position and the closed position; and e)comparing the position of the at least one exhaust valve sensed by thevalve position sensor to the desired one of the open position and theclosed position to determine if the at least one exhaust valve hasfailed again to reach the desired one of the open position and theclosed position.
 4. The exhaust valve system of claim 1, whereincontrolling the actuator to move the at least one exhaust valve to theintermediate position comprises controlling the actuator to move the atleast one exhaust valve to the intermediate position for a predeterminedamount of time; and once the at least one exhaust valve has been in theintermediate position for the predetermined amount of time, thecontroller is further programmed for: d) controlling the actuator toreattempt to move the at least one exhaust valve to the desired one ofthe open position and the closed position.
 5. The exhaust valve systemof claim 4, wherein, subsequent to step d), the controller is furtherprogrammed for: e) determining if the at least one exhaust valve hasfailed to reach the desired one of the open position and the closedposition based on the position of the at least one exhaust valve sensedby the valve position sensor.
 6. The exhaust valve system of claim 5,wherein, if at step e) the controller determines that the at least oneexhaust valve has failed again to reach the desired one of the openposition and the closed position, the controller is further programmedfor: f) controlling the actuator to move the at least one exhaust valveto the intermediate position for the predetermined amount of time; andthen g) repeating steps d) and e), and, if the at least one exhaustvalve has failed again to reach the desired one of the open position andthe closed position, step f), until: the controller determines at asubsequent instance of step e) that the at least one exhaust valve hasnot failed to reach the desired one of the open position and the closedposition; or steps d) and e) have been repeated a predetermined numberof times with the at least one exhaust valve having failed each time toreach the desired one of the open position and the closed position. 7.The exhaust valve system of claim 6, wherein: the predetermined amountof time is a first predetermined amount of time; and if steps d) and e)have been repeated the first predetermined number of times with the atleast one exhaust valve having failed each time to reach the desired oneof the open position and the closed position, the controller is furtherprogrammed for: h) maintaining the at least one exhaust valve in acurrent position for a second predetermined amount of time, thencontrolling the actuator to move the at least one exhaust valve to theintermediate position for a third predetermined amount of time, thesecond predetermined amount of time being greater than the firstpredetermined amount of time, the third predetermined amount of timebeing less than the first predetermined amount of time; i) controllingthe actuator to reattempt to move the at least one exhaust valve to thedesired one of the open position and the closed position; j) determiningif the at least one exhaust valve has failed again to reach the desiredone of the open position and the closed position based on the positionof the at least one exhaust valve sensed by the valve position sensor;and k) repeating steps i) and j), and, if the at least one exhaust valvehas failed again to reach the desired one of the open position and theclosed position, step h), until the controller determines at step j)that the at least one exhaust valve has not failed to reach the desiredone of the open position and the closed position.
 8. The exhaust valvesystem of claim 1, wherein the controller is further programmed for: l)performing step c) and any subsequent steps only if at step b): thecontroller determines that the at least one exhaust valve has failed toreach the desired one of the open position and the closed position; andthe position of the at least one exhaust valve is at less than apredetermined distance from the desired one of the open position and theclosed position; and if at step b): the controller determines that theat least one exhaust valve has failed to reach the desired one of theopen position and the closed position; and the position of the at leastone exhaust valve is at more than the predetermined distance from thedesired one of the open position and the closed position, then: m)controlling the actuator to move the at least one exhaust valve to oneof the open position and the closed position other than the desired oneof the open position and the closed position; and n) returning to stepa).
 9. The exhaust valve system of claim 8, wherein step m) comprisesmaintaining the at least one exhaust valve in the one of the openposition and the closed position other than the desired one of the openposition and the closed position for a predetermined amount of timebefore performing step n).
 10. The exhaust valve system of claim 7,wherein the desired one of the open position and the closed position isthe open position.
 11. The exhaust valve system of claim 1, wherein theintermediate position is or is approximately halfway between the openposition and the closed position.
 12. The exhaust valve system of claim1, wherein in the intermediate position the at least one exhaust valvedoes not affect port timing of the internal combustion engine and isexposed to exhaust gas flow.
 13. The exhaust valve system of claim 1,wherein each of the at least one exhaust valve comprises a blade. 14.The exhaust valve system of claim 1, wherein the actuator is anelectrical actuator.
 15. The exhaust valve system of claim 1, whereinthe controller determines that the at least one exhaust valve has failedto reach the desired one of the open position and the closed position ifthe position of the at least one exhaust valve is at more than apredetermined distance from the desired one of the open position and theclosed position.
 16. The exhaust valve system of claim 15, wherein thepredetermined distance is greater when the desired one of the openposition and the closed position is the open position than when thedesired one of the open position and the closed position is the closedposition.
 17. The exhaust valve system of claim 1, wherein thecontroller is further programmed for: entering a fault operation modeif, in response to the actuator attempting to move the at least oneexhaust valve to the desired one of the open position and the closedposition, the at least one exhaust valve has moved by less than apredetermined amount.
 18. The exhaust valve system of claim 17, whereinin the fault operation mode, the controller limits performance of theengine provided with the exhaust valve system.
 19. A method for cleaningat least one exhaust valve of an exhaust valve system for a two-strokeinternal combustion system, the method comprising: a) controlling anactuator operatively connected to the at least one exhaust valve toattempt to move the at least one exhaust valve to a desired one of anopen position and a closed position; b) determining if the at least oneexhaust valve has failed to reach the desired one of the open positionand the closed position based on a position of the at least one exhaustvalve sensed by a valve position sensor; and c) controlling the actuatorto move the at least one exhaust valve to an intermediate position whenthe at least one exhaust valve has failed to reach the desired one ofthe open position and the closed position, the intermediate position ofthe at least one exhaust valve being between the open position and theclosed position.
 20. The method of claim 19, wherein determining if theat least one exhaust valve has failed to reach the desired one of theopen position and the closed position comprises comparing the positionof the at least one exhaust valve sensed by the valve position sensor tothe desired one of the open position and the closed position.